Fannie Mae and Freddie Mac saw their retained portfolios shrink again in July as competition for mortgage assets remained strong. But there are signs that the government-sponsored enterprises might be poised to assume a more aggressive strategy toward MBS and other mortgage assets in the coming months. According to data tracked by Inside MBS & ABS, Fannie’s portfolio dropped 2.4 percent in July – the ninth straight month that the GSE has seen its numbers… [One data table included]